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<html><head><title>Techniques - Preparing a Scraper</title>

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<h1>Preparing a Scraper</h1>

<p>The scraper is the ultimate finshing tool before sanding. The hardness of a scraper steel is approximately 45 to 55 Rockwell. This makes them hard enough to hold the cutting edge, but soft enough to get them easily sharpened. Saw blades usually have this value, plane blades are usually in the area of 65 Rochwell.</p>

<p>Required tools:</p>

<ul>
<li>A straight file</li>
<li>Grinding (water) stones</li>
<li>Burnisher</li>
</ul>

<h2>Step 1: File the Cutting Edges</h2>

<p>To achieve a perfect right angle, you can set the blade in a vise at the exact height of the file handle, and use the file handle on the bench as guide while filing.</p>

<p class="imgbox"><img src="fig-001.jpg"/></p>

<p>A small bar with the height of the file handle helps to clamp the scraper with the cutting edge parallel to the bench.</p>
<p class="imgbox"><img src="fig-002.jpg"/></p>
<p>The file, resting on the handle on one side, and the scraper edge on the other side, is now parallel to the bench top, too.</p>
<p class="imgbox"><img src="fig-003.jpg"/></p>
<p>Now it is quite easy to file the cutting edge straight.</p>
<p class="imgbox"><img src="fig-004.jpg"/></p>
<p>Alternatively, you can use a squared piece of wood to guide a regular file on the side of the scraper blade.</p>
<p class="imgbox"><img src="fig-005.jpg"/></p>

<h2>Step 2: Honing the Edges</h2>

<p>Use a 3/4 inch piece of flat float glass as a base for the sharpening stones. Glued-on plexiglas strips prevent the stone from sliding away.</p>
<p class="imgbox"><img src="fig-006.jpg"/></p>
<p>Stones used: 1000, 8000, 16000 grit ceramic stones.</p>
<p class="imgbox"><img src="fig-007.jpg"/></p>
<p>Important: The stones <em>must</em> be flattened first. The tool to use is a diamond impregnated glass lapping plate.</p>
<p class="imgbox"><img src="fig-008.jpg"/></p>
<p>Start honing with the highes grit to avoid contamination of the fine stones with particles from the coarse stones.</p>
<p class="imgbox"><img src="fig-009.jpg"/></p>
<p>Rub until the surface is all white. The "smear" must be gone completeley.</p>
<p class="imgbox"><img src="fig-010.jpg"/></p>
<p>To maintain the square edge on the scraper, use a piece of square wood as a guide on the stone.</p>
<p class="imgbox"><img src="fig-011.jpg"/></p>
<p>Spend about 5 minutes on the 1000 grit stone, then check the surface: If it is matte grey and even, continue with the other edges.</p>
<p>Then switch to the 8000 grit stone. Clean everything well to avoid pollution of the finer stones with particles from the coarser stones. A few minutes on the 8000 grit stone until the matte grey is replaced by a more even shiny surface.</p>
<p>Same with the 16000 grit stone.</p>

<h2>Step 3: Polish the Sides</h2>
<p>The problem is to put even pressure on the side when rubing them on the stones. Use a piece of plastic (or MDF, protected by a coat of laquer), a little bit more narrow than the scraper, and stick it on the scraper with double-sided sticky tape.</p>
<p class="imgbox"><img src="fig-012.jpg"/></p>
<p class="imgbox"><img src="fig-013.jpg"/></p>
<p class="imgbox"><img src="fig-014.jpg"/></p>
<p class="imgbox"><img src="fig-015.jpg"/></p>
<p>When sliding the scraper over the stone, have a thin (< 1 mm) ruler on the stone to skew the scraper to a small angle. This reduces the area to be worked on to a small strip along the egde, and you don't have to work on the whole side. Which speeds up the process dramatically. Although the 90 degree angle to the edge surface is changed a very litte bit, this has no negative effect.</p>
<p class="imgbox"><img src="fig-016.jpg"/></p>
<p>Start with the 1000 grit stone to lay out the foundation, then continue with the 8000 and 16000 grit stones, quite like before with the edges.</p>
<p class="imgbox"><img src="fig-017.jpg"/></p>
<p class="imgbox"><img src="fig-018.jpg"/></p>

<h2>Step 4 Burnishing the Edges</h2>

<p>The burnisher must be harder than the scraper steel. Remember that burnishes have to be polished before they are used, even commercial ones are not ready-to-use. You can make a burnisher from an old file by grinding and polishing, but that takes quite a lot of time.</p>

<p>Burnishers with a circular sectional shape must be pressed down evenly, otherwise they create an uneven burr.</p>

<p>Use a litle bit of mineral oil for lubrication.</p>

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